Along with recent developments in IT (Information Technology) and the expansion of the mark, demands for a manufacturing apparatus that manufactures semiconductor devices, liquid-crystal display devices, and the like, have increased more and more. A particularly important component in manufacturing such devices is an exposure apparatus, which is used to form a pattern. Regarding the exposure apparatus, emphasis is put, not only on the exposure performance, but also, on the COO (Cost of Ownership), which supports the price competition of the finished products, i.e., the total operating cost of the manufacturing apparatus.
As an exposure apparatus, a one-to-one imaging exposure apparatus is generally used to illuminate a mask, to form a pattern within a predetermined region of the mask on a substrate within a good-image area in a projection imaging system. However, in the above one-to-one imaging exposure apparatus, the cost of a mask having a circuit pattern tends to greatly increase when the substrate size becomes larger. This is because one-to-one imaging basically requires a mask having the same size as that of a substrate. Accordingly, a reduction in cost of a mask is a serious problem in developing a large-sized display, such as a liquid crystal display.
Even in developing leading-edge VLSI submicron lithography, it is troublesome to reduce the cost of a mask, although its technical field is different from the liquid crystal display in line width, exposure area, and device specification. In the VLSI, the problem is not an increase in the size of a mask when the substrate size becomes larger, but an increase in the cost due to micropatterning. In particular, since the VLSI requires a large number of, e.g., twenty or more masks to be included in a mask set, mask costs present a serious problem.
To solve the above problem about the mask cost, a technique has been proposed that uses a mask lithography exposure apparatus (see, for example, U.S. Pat. No. 6,133,986).
U.S. Pat. No. 6,133,986 discloses a maskless lithography exposure apparatus that selectively reflects a portion of light using a DMD (Digital Micromirror Device) to expose the substrate surface.
When a glass substrate is used as an exposure target substrate, the working distance often varies due to undulations, typically having a size of about 20 μm, which are present on the surface of the glass substrate. If the working distance varies, a light source image is formed at a position that falls outside the surface of the exposure target substrate, resulting in a decrease in accuracy of the light source image formed on the surface of the exposure target substrate.
In U.S. Pat. No. 6,133,986, the working distance is detected using a light sensor. However, since image data obtained using the light sensor needs to be processed, the response speed naturally becomes low. Accordingly, a separate image data processing device is necessary. In addition, the optical path length needs to be assured. These requirements complicate the arrangement of the apparatus.